Quote:
Originally Posted by euromodder
The diameter does change - when measured from the contact point through the hub to the top) .
That's what lifts the vehicle when the tyres are pumped up.
What doesn't really change due to inflation pressure is the tyre's circumference.
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...true for the "unloaded" circumference, but NOT true for the "loaded" circumference.
...simple test: (1) measure the circumference of a tire; (2) paint a white spot on that tire; (3) drive exactly 5,280 ft measured mile at a slow speed and video record the whole distance; (4) review the video, counting exactly how many "tire revolutions" occur. I'll guarantee the number is
greater than the mathematical number derived from dividing the tires' circumference-in-feet into 5,280...the video "count" will be close to 3-4% higher than the mathematical number...and that
difference is because the "loaded" circumference is SMALLER than the "unloaded" circumference.
...unless you're driving on fuelly-slicks, circumference won't "grow" too much during normal driving...but it actually does at
high speeds with high profile sidewall tires.